Tool-holding apparatus, impact driver, and electric work machine

Abstract

A tool-holding apparatus ( 70 ) includes an engaging member ( 71 ) for engaging a tool accessory (B) and being movably supported in axial and radial directions in a rotational-output shaft ( 26 ) having an insertion hole ( 81 ) for holding the tool accessory (B). A first biasing member ( 72 ) biases the engaging member towards engagement with the engaging member. A bit sleeve ( 73 ) is movable in the axial direction along an outer-circumferential surface of the rotational-output shaft between a blocking position at which radial outward movement of the engaging member is blocked and a permitting position at which radial outward movement of the engaging member is permitted. A second biasing member ( 74 ) biases the bit sleeve toward the blocking position. A positioning part ( 75 ) is fixed on the outer-circumferential surface of the rotational-output shaft and stops the bit sleeve at the blocking position. The bit sleeve has a projection ( 88 ), which is disposed on the forward side of the first biasing member, extends inward in the radial direction, and slidably contacts the rotational-output shaft.

We claim: 
     
       1. A tool-holding apparatus comprising:
 a rotational-output shaft having an insertion hole configured to receive a mounting portion of a tool accessory; 
 at least one engaging member supported in the rotational-output shaft so as to be movable in an axial direction and a radial direction of the rotational-output shaft, the at least one engaging member being configured to engage with the tool accessory when the tool accessory is fully inserted into the insertion hole; 
 a compression coil spring biasing the at least one engaging member in a direction that causes the at least one engaging member to engage with the tool accessory; 
 a bit sleeve configured to be movable in the axial direction along an outer-circumferential surface of the rotational-output shaft between a blocking position, at which movement of the at least one engaging member outward in the radial direction is blocked, and a permitting position, at which movement of the at least one engaging member outward in the radial direction is permitted; 
 a second biasing member biasing the bit sleeve toward the blocking position; and 
 a positioning part fixed on the outer-circumferential surface of the rotational-output shaft and configured to stop axial movement of the bit sleeve at the blocking position; 
 wherein: 
 the bit sleeve has a projection, which is disposed on a forward side of the compression coil spring, and extends inward in the radial direction to a contacting, inner-circumferential surface that extends in parallel to a rotational axis of the rotational-output shaft, the contacting, inner-circumferential surface slidably contacting the rotational-output shaft at least at the permitting position and contacting the at least one engaging member at least at the blocking position; 
 one end of the compression coil spring in the axial direction presses against a surface that extends radially outward from the outer-circumferential surface of the rotational-output shaft, and the other end of the compression coil spring in the axial direction biases the at least one engaging member forward in the axial direction and away from the surface that extends radially outward from the outer-circumferential surface of the rotational-output shaft; 
 a tilted surface is provided on an inner-circumferential surface of the bit sleeve; 
 the tilted surface is arranged such that movement of the at least one engaging member outward in the radial direction against the tilted surface causes the bit sleeve to move axially forward relative to the rotational-output shaft against the biasing force of the second biasing member; 
 the tilted surface forms an angle with respect to a line parallel to the rotational axis of the rotational-output shaft within a range of 45° or greater and 90° or less; 
 the at least one engaging member is axially movable in a slotted hole defined in the rotational-output shaft; and 
 an axially-rearward wall of the slotted hole extends perpendicular to the rotational axis; 
 a recess is provided on the outer-circumferential surface of the rotational-output shaft; 
 a bottom of the recess has a diameter that is smaller than an outer diameter of a portion of the outer-circumferential surface of the rotational-output shaft that is rearward of the recess; 
 a wall is provided between the bottom of the recess and the portion of the outer-circumferential surface of the rotational-output shaft that is rearward of the recess, the wall extending perpendicular to a line parallel to the rotational axis of the rotational-output shaft and having an outer terminal edge that is disposed radially outward of the portion of the outer-circumferential surface of the rotational-output shaft that is rearward of the recess, and 
 the one end of the compression coil spring directly contacts the wall. 
 
     
     
       2. The tool-holding apparatus according to  claim 1 , wherein:
 the bit sleeve has a step provided on an end portion of an inner-circumferential portion of the bit sleeve in the axial direction; and 
 the step is arranged on the bit sleeve such that when the step makes contact with the positioning part, the bit sleeve is positioned at the blocking position. 
 
     
     
       3. The tool-holding apparatus according to  claim 2 , wherein:
 the bit sleeve has: 
 a first recess provided on the inner-circumferential surface of the bit sleeve contiguous with the tilted surface, the first recess being configured to permit movement of the at least one engaging member outward in the radial direction; and 
 a second recess that is contiguous with the first recess and surrounds the compression coil spring, the second recess being configured to permit movement of the compression coil spring radially outward of the outer-circumferential surface of the rotational-output shaft; 
 a third recess is provided in the outer-circumferential surface of the rotational-output shaft, the third recess having:
 a bottom having a diameter that is smaller than the outer diameter of the outer-circumferential surface of the rotational-output shaft; 
 a wall provided on one side of the bottom in the axial direction, the one end of the compression coil spring contacting the wall; and 
 a tapered portion provided on the other side of the bottom in the axial direction and being contiguous with the outer-circumferential surface of the rotational-output shaft; and 
 
 the compression coil spring is configured to always contact the wall of the third recess and to contact the bottom of the third recess at least when no tool accessory is inserted into the insertion hole. 
 
     
     
       4. The tool-holding apparatus according to  claim 1 , wherein the bit sleeve has:
 a first recess provided on the inner-circumferential surface of the bit sleeve and configured to permit movement of the at least one engaging member outward in the radial direction; and 
 a second recess that is contiguous with the first recess and surrounds the compression coil spring. 
 
     
     
       5. An electric work machine comprising:
 the tool-holding apparatus according to  claim 1 ; 
 a motor; and 
 the rotational-output shaft operably driven by the motor; 
 wherein the tool-holding apparatus is provided at a tip portion of the rotational-output shaft. 
 
     
     
       6. The tool-holding apparatus according to  claim 1 , wherein the tilted surface is a single continuous inclined surface that extends axially rearward and radially outward from the contacting, inner-circumferential surface of the projection to a portion of the inner-circumferential surface of the bit sleeve that is parallel to the rotational axis of the rotational-output shaft. 
     
     
       7. The tool-holding apparatus according to  claim 6 , wherein:
 in the blocking position of the bit sleeve, a first portion of the contacting, inner-circumferential surface that is directly circumferentially adjacent to the slotted hole contacts the outer-circumferential surface of the rotational-output shaft, and 
 in the permitting position of the bit sleeve, a second portion of the contacting, inner-circumferential surface that is directly axially forward of the slotted hole contacts the outer-circumferential surface of the rotational-output shaft. 
 
     
     
       8. A tool-holding apparatus, comprising:
 a rotational-output shaft having an insertion hole configured to receive a mounting portion of a tool accessory; 
 at least one engaging member supported in the rotational-output shaft so as to be movable in an axial direction and a radial direction of the rotational-output shaft, the at least one engaging member being configured to engage with the tool accessory when the tool accessory is fully inserted into the insertion hole; 
 a compression coil spring biasing the at least one engaging member in a direction that causes the at least one engaging member to engage with the tool accessory; 
 a bit sleeve configured to be movable in the axial direction along an outer-circumferential surface of the rotational-output shaft between a blocking position, at which movement of the at least one engaging member outward in the radial direction is blocked, and a permitting position, at which movement of the at least one engaging member outward in the radial direction is permitted; 
 a second biasing member biasing the bit sleeve toward the blocking position; and 
 a positioning part fixed on the outer-circumferential surface of the rotational-output shaft and configured to stop axial movement of the bit sleeve at the blocking position; 
 wherein: 
 the bit sleeve has a projection, which is disposed on a forward side of the compression coil spring, and extends inward in the radial direction to a contacting, inner-circumferential surface that extends in parallel to a rotational axis of the rotational-output shaft, the contacting, inner-circumferential surface slidably contacting the rotational-output shaft at least at the permitting position and contacting the at least one engaging member at least at the blocking position; 
 one end of the compression coil spring in the axial direction presses against a surface that extends radially outward from the outer-circumferential surface of the rotational-output shaft, and the other end of the compression coil spring in the axial direction biases the at least one engaging member forward in the axial direction and away from the surface that extends radially outward from the outer-circumferential surface of the rotational-output shaft; 
 a tilted surface is provided on an inner-circumferential surface of the bit sleeve; 
 the tilted surface is arranged such that movement of the at least one engaging member outward in the radial direction against the tilted surface causes the bit sleeve to move axially forward relative to the rotational-output shaft against the biasing force of the second biasing member; 
 the tilted surface forms an angle with respect to a line parallel to the rotational axis of the rotational-output shaft within a range of 45° or greater and 90° or less; 
 a third recess is provided on the outer-circumferential surface of the rotational-output shaft and supports the compression coil spring; and 
 the third recess has:
 a bottom having a diameter that is smaller than the outer diameter of the outer-circumferential surface of the rotational-output shaft; 
 a wall provided on one side of the bottom in the axial direction, the one end of the compression coil spring contacting the wall; and 
 a tapered portion provided on the other side of the bottom in the axial direction and being contiguous with the outer-circumferential surface of the rotational-output shaft. 
 
 
     
     
       9. An impact driver comprising:
 a motor; 
 a hammer, which is rotated by the motor; and 
 an anvil part, which is impacted by the hammer in a rotational direction and is disposed on a forward side of the hammer in an axial direction; 
 wherein: 
 the anvil part includes: an anvil configured to contact the hammer in the rotational direction; a substantially hexagonal hole extending within the anvil in the axial direction; a slotted hole that extends outward in the radial direction from the substantially hexagonal hole; a ball disposed in the slotted hole so as to be movable in the axial and radial directions; a first elastic body biasing the ball forwardly in the axial direction relative to the anvil; a bit sleeve disposed around the anvil and the ball and configured to be movable relative to the anvil in the axial direction; and a second elastic body biasing the bit sleeve rearwardly in the axial direction relative to the anvil; 
 the anvil part is configured such that, at any axial position of the bit sleeve relative to the anvil, in response to a tool accessory being inserted into the substantially hexagonal hole, the first elastic body is at least radially outwardly deformable to urge the ball to automatically fall into a recess defined in a mounting portion of the tool accessory; 
 the anvil includes:
 a wall that extends radially inward from an outer-circumferential surface of the anvil, a first axial end of the first elastic body contacting the wall, 
 a bottom that extends from a radially-inward-most end of the wall in parallel to the axial direction, and 
 a tapered portion that connects the bottom and the outer-circumferential surface of the anvil in an inclined manner; and 
 
 a second axial end of the first elastic body contacts the ball. 
 
     
     
       10. The impact driver according to  claim 9 , wherein an axially rearward portion of the bit sleeve is configured to permit movement of the ball outward in the radial direction beyond an outer circumferential surface of the anvil. 
     
     
       11. A power tool, comprising:
 a rotational-output shaft having an insertion hole, which extends in an axial direction and is configured to receive a mounting shaft of a tool accessory, and a slotted hole extending in a radial direction from the insertion hole to an outer-circumferential surface of the rotational-output shaft; 
 a ball disposed in the slotted hole so as to be movable in the axial and radial directions of the rotational-output shaft, the ball and the slotted hole being configured such that the ball is engageable in a first circumferential groove defined in the tool accessory when the tool accessory is fully inserted into the insertion hole; 
 a first biasing member disposed in a second circumferential groove defined in an outer-circumferential surface of the rotational-output shaft and applying a first biasing force to the ball at least forwardly in the axial direction; 
 a bit sleeve surrounding the outer-circumferential surface of the rotational-output shaft and having a projection that extends radially inward from an inner-circumferential surface of the bit sleeve, the projection being configured to slidably contact the outer-circumferential surface of the rotational-output shaft; 
 a second biasing member disposed on the outer-circumferential surface of the rotational-output shaft and applying a second biasing force to the bit sleeve rearwardly in the axial direction; and 
 a stopper extending radially outward from the outer-circumferential surface of the rotational-output shaft, the stopper being arranged on the rotational-output shaft at an axial position that defines a blocking position of the bit sleeve; 
 wherein: 
 the bit sleeve is configured to be movable in the axial direction relative to the rotational-output shaft from the blocking position, at which the projection radially surrounds the ball and blocks movement of the ball radially outward of the outer-circumferential surface of the rotational-output shaft, to a permitting position, at which the projection does not radially surround the ball and thereby radially outward movement of the ball radially outward of the outer-circumferential surface of the rotational-output shaft is not blocked by the projection, and vice versa; 
 the second circumferential groove includes:
 a wall that extends radially inward from the outer-circumferential surface of the rotational-output shaft, a first axial end of the first biasing member contacting the wall, 
 a bottom that extends from a radially-inward-most end of the wall in parallel to the axial direction, and a second axial end of the first biasing member contacts the ball 
 a tapered portion that connects the bottom and the outer-circumferential surface of the rotational-output shaft in an inclined manner; and 
 
 a second axial end of the first biasing member contacts the ball. 
 
     
     
       12. The power tool according to  claim 11 , wherein the second circumferential groove in the rotational-output shaft is contiguous with the slotted hole. 
     
     
       13. The power tool according to  claim 11 , wherein the first biasing member is configured to also apply a radially-inward biasing force to the ball. 
     
     
       14. The power tool according to  claim 13 , wherein:
 the first biasing member has a resting winding radius relative to an axial center of the rotational-output shaft when no force is being applied against the first biasing member, and 
 the second circumferential groove, the ball and the slotted hole are configured such that, when a tool accessory is not inserted in the insertion hole and the ball is located as its radially inward-most position, the resting winding radius of the first biasing member is greater than a radial distance between the axial center of the rotational-output shaft and a radially-outermost edge of the ball. 
 
     
     
       15. The power tool according to  claim 14 , wherein:
 the projection is disposed between the first and second biasing members in the axial direction; and 
 the second biasing member contacts a first radially-extending surface of the projection. 
 
     
     
       16. The power tool according to  claim 15 , wherein:
 a third circumferential groove is defined in an inner circumferential surface of the bit sleeve axially rearward of the projection; 
 a tilted surface is defined on a second surface of the projection that is axially opposite of the first radially-extending surface, the tilted surface being contiguous with the third circumferential groove; 
 the tilted surface forms an angle with respect to a line parallel to a rotational axis of the rotational-output shaft of 45°-90°; 
 the tilted surface is arranged such that radially-outward movement of the ball against the tilted surface causes the bit sleeve to move axially forward relative to the rotational-output shaft against the second biasing force of the second biasing member; and 
 the third circumferential groove is configured to permit the first biasing member and the ball to move radially outward of the outer-circumferential surface of the rotational-output shaft when the bit sleeve is disposed at the permitting position. 
 
     
     
       17. The power tool according to  claim 16 , wherein the second biasing member has a resting winding radius that is greater than the resting winding radius of the first biasing member. 
     
     
       18. The power tool according to  claim 11 , wherein the tool accessory is insertable into the insertion hole regardless of the axial position of the bit sleeve relative to the rotational-output shaft.